Changes in Shareholders' Equity - Changes in Minority Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Comprehensive income (loss):
Amortization of prior service cost and unrecognized gains and losses included in total benefit cost, net of tax of $0 and $0 in 2015	$ 16	$ 18	$ 32	$ 37
Decrease (increase) in net actuarial losses, net of tax of $0 and $0 in 2015	1	24	1	24
Deferred derivative gains (losses), net of tax of $0 and $0 in 2015	9	(3)	3	10
Reclassification adjustment for amounts recognized in income, net of tax of $0 and $0 in 2015	(5)	(9)	(8)	(13)
Total comprehensive income (loss)	1	35	13	(15)
Changes in Minority Equity Presented Outside of Shareholders' Equity (Textuals)
Tax on foreign currency translation	(3)	10	14	(24)
Tax on amortization of prior service cost and unrecognized gains and losses included in total benefit cost	(8)	(9)	(16)	(18)
Tax on decrease (increase) in net actuarial losses	1	11	0	11
Tax on deferred derivative gains (losses)	1	0	0	2
Tax on reclassification adjustment for amounts recognized in income	$ 1	1	$ 2	2
Minority Shareholders' Equity - Redeemable
Changes in Minority Equity presented outside of Shareholders' Equity
Balance at beginning of period		539		582
Comprehensive income (loss):
Net income		7		16
Foreign currency translation, net of tax of $0 and $0 in 2015		23		(32)
Amortization of prior service cost and unrecognized gains and losses included in total benefit cost, net of tax of $0 and $0 in 2015		1		2
Decrease (increase) in net actuarial losses, net of tax of $0 and $0 in 2015		2		2
Deferred derivative gains (losses), net of tax of $0 and $0 in 2015		(1)		1
Reclassification adjustment for amounts recognized in income, net of tax of $0 and $0 in 2015		(2)		(2)
Other comprehensive income (loss)		23		(29)
Total comprehensive income (loss)		30		(13)
Balance at end of period		569		569
Changes in Minority Equity Presented Outside of Shareholders' Equity (Textuals)
Tax on foreign currency translation		0		0
Tax on amortization of prior service cost and unrecognized gains and losses included in total benefit cost		0		0
Tax on decrease (increase) in net actuarial losses		0		0
Tax on deferred derivative gains (losses)		0		0
Tax on reclassification adjustment for amounts recognized in income		$ 0		$ 0